Increased user stack size, fiddling with error recovery

[tpg/acess2.git] / Kernel / arch / x86 / proc.asm

diff --git a/Kernel/arch/x86/proc.asm b/Kernel/arch/x86/proc.asm
index 1cf1f96..ebc1664 100644 (file)
--- a/Kernel/arch/x86/proc.asm
+++ b/Kernel/arch/x86/proc.asm
@@ -84,7 +84,7 @@ Proc_ReturnToUser:
        ; EAX is the current thread
        mov ebx, eax
        mov eax, [ebx+40]       ; Get Kernel Stack
-       sub eax, KSTACK_USERSTATE_SIZE  
+       sub eax, KSTACK_USERSTATE_SIZE
        
        ;
        ; NOTE: This can cause corruption if the signal happens while the user
@@ -92,12 +92,43 @@ Proc_ReturnToUser:
        ; Good thing this can only be called on a user fault.
        ;
        
+       ; Validate user ESP
+       ; - Page Table
+       mov edx, [eax+KSTACK_USERSTATE_SIZE-12] ; User ESP is at top of kstack - 3*4
+       %if USE_PAE
+       %error PAE Support
+       %else
+       mov ecx, edx
+       shr ecx, 22
+       test BYTE [0xFC3F0000+ecx*4], 1
+       jnz .justKillIt
+       %endif
+       ; - Page
+       mov ecx, edx
+       shr ecx, 12
+       test BYTE [0xFC000000+ecx*4], 1
+       jnz .justKillIt
+       ; Adjust
+       sub edx, 8
+       ; - Page Table
+       %if USE_PAE
+       %else
+       mov ecx, edx
+       shr ecx, 22
+       test BYTE [0xFC3F0000+ecx*4], 1
+       jnz .justKillIt
+       %endif
+       ; - Page
+       mov ecx, edx
+       shr ecx, 12
+       test BYTE [0xFC000000+ecx*4], 1
+       jnz .justKillIt
+       
        ; Get and alter User SP
-       mov ecx, [eax+KSTACK_USERSTATE_SIZE-12]
-       mov edx, [ebx+60]       ; Get Signal Number
-       mov [ecx-4], edx
-       mov [ecx-8], DWORD User_Syscall_RetAndExit
-       sub ecx, 8
+       mov ecx, edx
+       mov edx, [ebx+60]       ; Get Signal Number from TCB
+       mov [ecx+4], edx        ; Parameter (Signal/Error Number)
+       mov [ecx], DWORD User_Syscall_RetAndExit        ; Return Address
        
        ; Restore Segment Registers
        mov ax, 0x23
@@ -113,6 +144,14 @@ Proc_ReturnToUser:
        push ebp        ; EIP
        
        iret
+       
+       ; Just kill the bleeding thing
+       ; (I know it calls int 0xAC in kernel mode, but meh)
+.justKillIt:
+       xor eax, eax
+       xor ebx, ebx
+       dec ebx
+       int 0xAC
 
 [global GetCPUNum]
 GetCPUNum:
@@ -122,6 +161,7 @@ GetCPUNum:
        shr ax, 3       ; ax /= 8
        ret
 
+; Usermode code exported by the kernel
 [section .usertext]
 User_Syscall_RetAndExit:
        push eax